Researchers Investigate Explosion of Sea Pickles off Northwest Coast

Posted on July 5, 2017

Pyrosomes or sea pickles found off Oregon Coast

The number of sea pickles (pyrosomes) has exploded off the Northwest coast over the past thee years. The tubular translucent creatures were rarely seen in the region until about two years ago. This year the pyrosomes have exploded in numbers. Researchers from the NOAA Fisheries' Northwest Fisheries Science Center, Oregon State University and the University of Oregon are trying to figure out why.

There are so many pyrosomes in the waters off Oregon that they are clogging up fishing gear. Scientists found that a five minute underwater tow of a research net off the Columbia River in May retrieved about 60,000 of the creatures. The pyrosomes vary greatly in size ranging from a few inches to over two feet. The pyrosomes are larger and more abundant farther offshore.

Hilarie Sorensen, a University of Oregon graduate student, says, "At first we didn’t know what to make of these odd creatures coming up in our nets but as we headed north and further off shore, we started to get more and more. We began counting and measuring them to try to get a better understanding of their size and distribution related to the local environmental conditions."

The researchers say in a Northwest Fisheries Science Center release, "Pyrosomes are as mysterious as they are strange. Each pyrosome is made up of individual zooids – small, multicellular organisms - linked together in a tunic to form a tube-like colony that is closed on one end. They are filter feeders and use cilia to draw plankton into their mucous filter. Some bony fish, dolphins and whales are known to eat pyrosomes, but scientists know little about their role in the offshore ecosystem or how they may affect the food web in areas where they are now appearing in such high densities."

A CNN story on the sea pickles says one theory is that warming waters may be the cause as the creatures are usually found in more tropical waters. This underwater video captured by the NOAA research ship Bell M. Shimada found "legions of pyrosomes in extremely high densities from approximately 40 to 200 miles off of the Oregon Coast."



Image: Hilarie Sorenson/University of Oregon


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